<!DOCTYPE html>
    <html>
        <head>
            <title></title>
            <script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.3.20/angular.js"></script>
            <script src="controller.js"></script>
        </head>
        <body ng-app="app">
            <div ng-controller="emp">
                <div>
                    Value of a is {{a}},
                    but you can change
                    <input type="text" ng-model="a"><br>
                    
                    Value of b is {{b}},
                    but you can change
                    <input type="text" ng-model="b">
                </div>
                
                Sum= {{sum}}<br>
                <button ng-click="doSum()">Calculate</button>
            </div> 
        </body>
    </html>